1. Field of the Invention
The present invention relates to an electric fuse cut-out circuit of the cylindrical type or knife type.
2. Description of the Prior Art
Different fuse cartridge structures are already known used for protecting electric apparatus against over currents and short circuits. One of them, of cylindrical type, comprises a cylindrical insulating body ending in two conducting capsules or caps, also called end pieces, and in which is disposed, on the one hand, a fuse wire connected electrically to the two end pieces and, on the other a sand filling whose purpose is to dissipate the electric arc energy created on the appearance of an overcurrent or a short circuit. In fact, in the presence of this type of electric fault, the fuse wire splits into two parts between which an electric arc is created which causes both the sand and the fuse wire to melt. By melting the sand cools the arc so as to extinguish it completely, thus breaking the electric circuit.
Another known fuse cartridge structure, this time of the knife type, and operating in an identical way to that described above comprises, on the one hand, an insulating body of a substantially parallelepipedic shape in which are disposed, as before, the fuse element (blade or strip) and the sand and, on the other hand, two end pieces or conducting knives provided perpendicularly on two opposite end faces of the body and connected electrically to the fuse element.
However, these fuse cartridge structures, whether cylindrical or with knives, have drawbacks. In fact, correct operation of the fuse cartridge implies among other things that the sand is pure and that its grain size is very precise for it varies depending on each type of cartridge. Such conditions require then numerous checks and measurements which are time consuming and complicated to carry out. In addition, the fact of having sand does not guarantee for the fuse cartridge a total insulation between the two parts of the fuse element once split.